Method and apparatus for heating thermoplastic yarn

ABSTRACT

The disclosure relates to a method and apparatus for heating thermoplastic yarn wherein yarn is passed in contact with a heater surface and a gaseous atmosphere enveloping the yarn and the surface is maintained at a temperature which alters or precludes the descending temperature gradient away from the heater surface which is characteristic of yarn heaters presently used in the art. In particular the disclosure concerns a heater having a revolvable roll or other movable heating surface mounted within an enclosure. Yarn is introduced into the enclosure through a small tube and passed in contact with the movable heating surface and then withdrawn from the enclosure through another small tube. A heating element is mounted within the enclosure to heat the air therein. The roll has fanblades mounted at one end. The movable heating surface is driven by shaft means which is connected to the yarn processing machine with which the heater is associated and rotation of the roll causes the fan to rapidly circulate heated air within the enclosure. Baffles are provided to deflect the heated air over the surface of the revolving roll.

ilnited States atent [191 Seem et a1.

[ METHOD AND APPARATUS FOR HEATING THERMOPLASTIC YARN [76] Inventors: Warren A. Seem, Box 4939, Nassau,

Bahamas; Robert F. Conrad, Box 5341 Falmouth Rd., Washington, DC.

Filed: Mar. 20, 1970 Appl. No.: 28,269

Related US. Application Data [63] Continuation of Ser. No. 722,592, April 19, 1968,

McIntosh et a1 57/34 Apr. 16, 1974 Primary Examiner-Werner l-l. Schroeder [5 7] ABSTRACT The disclosure relates to a method and apparatus for heating thermoplastic yarn wherein yarn is passed in contact with a heater surface and a gaseous atmosphere enveloping the yarn and the surface is maintained at a temperature which alters or precludes the descending temperature gradient away from the heater surface which is characteristic of yarn heaters presently used in the art. In particular the disclosure concerns a heater having a revolvable roll or other movable heating surface mounted within an enclosure. Yarn is introduced into the enclosure through a small tube and passed in contact with the movable heating surface and then withdrawn from the enclosure through another small tube. A heating element is mounted within the enclosure to heat the air therein. The roll has fanblades mounted at one end. The movable heating surface is driven by shaft means which isconnected to the yarn processing machine with which the heater is associated and rotation of the roll causes the fan to rapidly circulate heated air within the enclosure. Baffles are provided to deflect the heated air over the surface of the revolving roll.

13 Claims, 22 Drawing Figures PATENTEDAPR 1 6 m SHEET 1 BF 5 J w q 15.14; x4 ,I I if x PATENTEI] APR 16 i974 SHEET 5 0F 5 METHOD AND APPARATUS FOR HEATING THERMOPLASTIC YARN This application is a Continuation of application No. 722,592 filed Apr. 19, 1968, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to the field of methods and apparatus for heating thermoplastic textile yarns in the course of processing them into false twisted yarns and set yarns made therefrom.

In the heat processing of travelling thermoplastic yarns, many types and forms of heating devices have been used as a source of heat to heat the yarn. So called contact heaters (such as disclosed in U. S. Pat. Nos. 3,283,414; 2,864,229; 3,099,065; 3,292,354 and 3,289,400), radient heaters (such as disclosed in U. S. Pat. Nos. 2,803,109 and 2,896,060) and convection heaters (in which heated air is circulated through a long rectangular box through which a number of ends of yarn are passed) are in use in the art but so called stationary contact heaters are the most widely used.

In the yarn processing industry a contact heater is generally understood to refer to a heater in which a yarn is intended to run in contact with a heated surface, regardless of the extent to which the yarn is in fact heated by conduction of heat from said heated surface and whenever the expression contact heater is used herein this meaning is intended to apply.

Also in the industry a radient heater is generally understood to refer to a heater in which the yarn is intended to run in close proximity to a heated surface, usually within a tube, regardless of the extent to which the yarn is in fact heated by radiation of heat from said heated surface and wherever the expression radient heater is used herein this meaning is intended to apply.

in the use of convection heaters wherein the heat is generated at a point quite remote from where the yarn passes through the heater the yarn must in fact be heated primarily by convection but we have found that when heat is transferred to a travellingyam from a contact heater, said heat transfer is not due to heat conduction alone but is also to a considerable extentdue to heat radiation and/or convection and similarly the heat transfer from a radient heater to a travelling yarn is not due to heat radiation alone but is due in part to heat convection. However, regardless of the types and forms .or mode of operation of heating devices presently used, the length of the heater required to obtain the desired ro required heat effect upon the thermoplastic yarn travelling at economically high rates of linear speed, have necessarily been so long that consequential high cost of producing the machinery, high electrical consumption, lack of ease of operation and excessive floor space required, has diminished the economic value of high speed machinery.

It has been noticed that with all contact heaters, even those considered to be well insulated, there is a descending temperature gradient away from the heating contact surface with the result that the major parts of the yarn not in tangential contact with the heating surface of the heater are not heated by radiation and/or convection of heat from the heating surface to the same extent as the portion of yarn that is in contact with the heating surface is heated by conducted heat.

It has been observed also that a factor which effects the efficiency of stationary contact heaters presently used to heat travelling thermoplastic textile yarns during such yarn operations is the extent to which the travelling yarn remains in constant physical contact with the heater surface. A vibratory motion occasioned by the vibrations of the twisting of the yarn and/or the rapid drawing of the yarn across the stationary heater of different co-efficient of friction than that of the yarn tends to reduce the physical contact of the yarn with the heater surface. This particular disadvantage does not apply to contact heaters which comprise a revolving roll but up to the moment these have been used relatively little because of the high cost of manufacturing a system which will satisfactorily heat a revolving element and lack of appreciation of the advantage of using such rolls where provisions are made to preclude or materially reduce a descending temperature gradient away from the surface of the roll.

SUMMARY OF THE INVENTION We have found that efficiency and performance of contact heaters can be improved, and therefore can be made shorter and smaller than heaters according to present designs capable of attaining comparable results, by making special provisions to heat the portions of yarn which are not in tangential physical contact with the surface of the contact heater, and have found that these special provisions also make it possible to practically and economically heat the surface of a revolving roll which then serves as the contact heater surface. We have also found that when a revolving roll is heated in such manner the heat to the revolving surface can be supplemented in an economical and practical manner. In general, we have found that efiicient and effective heating of the yarn is attained when the special provisions for heating the portion which is not in tangential contact with the contact heater surface are designed to preclude a descending temperature gradient in the direction away from the contact heater surface. We have found that this principle makes practical the use of revolving roll heaters wherein the vibratory contact between the heater surface and the yarn can be reduced by moving the heater surface in the same direction as the yarn. This also provides a more constant and intimate contact with the heater surface and an increased transfer'of heat by the effective'mode of conductance. This also permits making one or more convolutions or wraps of yarn around the heating surface without adding tension to the yarn and thereby permitting the necessary heating of a rapidly moving yarn in a much shorter overall length of heater body. The invention also makes possible an efficient and inexpensive means and method for maintaining, if desired, the whole of the interior of the heater at the same level of temperature by mechanically agitating and/or circulating the atmosphere within the heater chamber. This feature provides the further advantage of establishing in the heater a movement of the atmosphere which makes it possible to circulate portions of it through a system for removing from the heater chamber materials volatilized and/or thrown off by the yarn during the course of its heat treatment.

The principle of the invention may also be applied to provide an economical and efiicient heater having two separate chambers which may be maintained at different temperature levels whereby yarn passing through the heater may be subjected in sequence to different processing conditions of temperature and tension and may also be made to pass outside the heater enclosure to cool it in the course of its travel from one of the treatment chambers to the other. The heater according to the present invention, particuarly for use in a false twisting operation, may also be provided with a yarn shrinking zone ahead of the contact heating surface, and a further. yarn heating zone thereafter. Such a heater may also include means for stopping, within the heater, the false twist running back from a false twisting device. The invention also provides a variety of types of contact heater surfaces and means for maintaining the desired yarn path over heater surfaces.

' DESCRIPTION OF THE DRAWINGS FIG. 1 a vertical section transversely across the axis of the revolvable heater roll at about its midpoint, showing also in section the volatile condenser tube associated with the heater; I

FIG. 2 is a transverse section axially through the revolvable roll showing in section both the block on which the revolvable roll is mounted and also baffles within the enclosure;

FIG. 3 is a front elevational view of the fan which is mounted on the end of the revolvable roll as shown in FIG. 2; I I

FIG; 4 -is a view like FIG. 2 except it shows Calrodsmounted in the block which supports the shaft which turns the revolvable roll and which extend into the cylindrical heat sink within the revolvable roll;

FIG. 5 shows an alternative form of contact heater surface which may be sustituted for the revolvable roll illustrated in FIGS 1, 2 and 4;

FIG. 6 illustrates another form of contact heater surface, consisting of four spaced apart rolls, which may also be substituted for the revolvable roll shown in F1651, nd

' FIG. 7 is a schematic of a false twisting machine showing the manner in which the heater of the present invention can be used with such machine;

FIG. 8 is a schematic of a machine of the kind which produces false twist yarn and thereafter post treatesit and which illustrates the manner in which the heater of I the present invention may be employed in both'the false twisting and post treating sections of such a machine;

FIG. 9 is a schematic illustrating the manner in which a heater according to the present invention may be used on an uptwisting machine;

FIGS. 10 and 11 illustrate the manner in which the heater according to the present invention may be used on constant speed coning machines;

' FIG-12 is a side elevational view of a twist trapper shown mounted onthe pins of a yarn separater bar as sociated with a revolving roll of the kind illustrated in FIGSQI and 2;

FIG. 13 is a top elevational view of the same twist pp FIG. 14- is a front elevational view of the frame of the samef twist trapper;

"FIG. 15 is a top elevational view of a heated roll having a perforate surface through which heated air within the heater enclosure may be passed;

FIG. 16 is a rear'end view of the roll shown in FIG. 15showing the ends of the squirrel-cage like blades which cause air within the enclosure to pass through the perforate surface of the roll when it is revolved;

FIG. 17 is a front end view of the roll shown in FIG. 15 also showing ends of the squirrel-cage like blades and showing in front elevation the fan blades mounted on the front end of the roll;

FIG. 18 illustrates a further kind of contact heater surface which may be employed in lieu of the revolvable roll shown in FIGS. 1 and 2 and which comprises a belt passing around two spaced rolls;

FIG. 19 is a view part in section and part in perspective of a heater roll having a fan blade at its end which is mounted on a shaft which is concentric within the shaft which drives the roll and arranged to be rotated in opposite direction;

FIG. 20 is a schematic view of a well known selfadvancing Godet type roll which may be used in lieu of the roll shown in FIGS. 1 and 2;

FIG. 21 is a schematic view of a heater design having two separate chambers which may be maintained at different temperature levels and which includes means to regulate the volume of heated aircirculating between the two chambers; and

FIG. 22 is a view similar to that of FIG. 21 which also illustrates means for passing the yarn outside the heater enclosure to cool it in the course of its passage from one heater chamber to the other.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The heater illustrated in FIG. 1 comprises an enclosure generally indicated at 10 which is made up of a body of insulation 11 and an exterior metal shell 12. This heater enclosure, as may be seen better in FIG. 2, is removably mounted on a metal plate 13. The rear inner wall of the enclosure is provided with a metal band 14 which slips over the outer periphery of the plate 13 and holds the enclosure in position on the plate. A rotatably mounted heater roller generally indicated at 15 is supported on the plate 13 and thus within the enclosure when it is mounted as described. The roll illustrated in FIGS. 1 and 2 comprises the cup shaped member 16 which is fixed to the shaft 17 by screw 18. The rotation of the shaft will therefore cause rotation of the heater roll and such'rotat ion is imparted to the shaft by means of a gear19 which is designedto be engaged by a corresponding driving gear carried by the machine with which the heater is associated. The shaft 17 extends through and is supported by hearing 20 which is positioned in an aperture in the plate 13. A cylindrical plug 21 is supported on the inner wall of the plate 13 by screws 22, 23 and this plug is dimensioned so that it fits freely but snugly within the shell 16 of the heater roll. The plug is formed of a metal which will retain heat so that the plug may act as a heat sink. An insulating washer 24 is interposed between the back side of the plug and the plate 13 to minimize loss of heat through the plate. A fan blade 25 which may be of the kind illustrated in FIG. 3, is fixed to the circular end wall of the heater roll 16. This 'fan is shown fixed to the roll and so that the air which is caused to circulate within the heater enclosure constantly moves across the element picking up heat which is then carried to the surface of the heated roll and yarn in contact with the surface.

If desired, a metal separator may be placed between the resistance element and the heated roll, the arrangement being such that the circulating air passes over the resistance element behind the separator and then in the main chamber of the enclosure but the radiation to the heated roll and the yarn in contact therewith is from the separator which has a width at least equal to the length of the heated roll. Such an arrangment minimizes whatever localized effect may be produced by radiation issuing from an element which is relatively narrow compared to the length of the roll.

The heater roll is rotated in the direction of the yarn travel causing a rotation of the fan 25 which mechanically agitates and circulates the heated atmosphere within the interior of the heater chamber. This action continually moves the enclosed atmosphere over all exposed surfaces within the heater chamber, including the resistance element 28 and all other interior surfaces; thus tending to create a uniform temperature throughout the chamber. The movement of the air within the chamber at a substantial velocity also results in a more effective heat exchange between the yarn and the atmosphere by continuously sweeping away from the yarn the portion of the atmosphere which has delivered-up some part of its heat energy to the yarn. The moving atmosphere also makes it possible to pass an increased volume of heated atmosphere and therefore an increased quantity of heat energy, into contact with the yarn in the course of its passage through the heater. The provision of a source of heat 28 which is external to the heated roll establishes the condition wherein the atmosphere immediately adjacent to heater surface is at a temperature at least as high as that of the surface. Consequently, although the circumference of the yarn in tangential contact with the surface will have heat transferred to it by the effective mode of conduit, the other portions of the periphery of the yarn will be continually in contact with a moving body of heated atmosphere at a temperature at least as high as that of the heater surfacepTherefo re, there is established within the heater chamber a condition which materially alters or precludes a decreasing temperature gradient in the direction away from the surface of the heater roll as compared to that which would exist in the same heater if the same quantity of heat energy were employed to heat the roll alone as is done in all heater roll devices now in use in the art.

In the heater shown in FIGS. 1 and 2, the yarn Y enters the heater through a tube 29, preferably of a diameter not more than about two or three times that of th diameter of the yarn. This tube is aligned in the heater enclosure so that the yarn passing through it approaches the heated roll tangentially. The yarn may be wrapped one or more times about the roll and then led out of the enclosure through the tube 29A which is of the same character as tube 29. FIG. 2 illustrates tube 29 connected into an electric circuit 30 as a resistance which causes heating of the tube. This feature may be employed when it is desired to pre-heat the yarn entering the heater enclosure, particularly in instances where it is desired to subject the yarn to some shrinkage before it makes contact with the heater surface. A

similar circuit may be applied to the exit tube 30 in order to lengthen out the effective heating zone on the exit side of the heater surface. The use of such tubes makes possible increasing the effective length of a given heater without substantially increasing its mass.

FIG. 1 illustrates a heater having incorporated into it a device for collecting and removing materials volatilized or thrown off from the yarn in the course of its treatment within the heater. This arrangement includes a conduit 31 which at one end opens into an upper portion of the heater at 32. The conduit extends through the insulation 11 of the heater enclosure and downwardly along the outisde of the enclosure, with its lower end re-entering and opening at 33 into the lower part of the heater enclosure. The portion of the spin finish condensing and/or filtering tube which is positioned outside of the heater enclosure is shown encased in insulation 34 which is enclosed by metal cover 35. The effectiveness of insulation 34 is such that the body of the condensing tube is at a temperature below that which the volatiles from the yarn will condense, the insulation being used to prevent the tube from dropping substantially below the condensation temperature and thus unnecessarily dissipating heat from the closed heater system. Volatiles condensing in the tube migrate to the collector tube 36, and'from there, it may be periodically withdrawn by opening the valve 37. If desired, a filter plug may be inserted into the conduit 31, for example by pushing it up through tube 36 so that its upper end is positioned in conduit 31', to filter lint or other solids from the atmosphere flowing through the conduit. A flow regulating valve 38 is located approximately mid-way along the length of the condensing tube 31 and serves to regulate the volume of the atmosphere passing through the tube.

A thermosensing element 39 extends into the heater enclosure and is positioned relatively close to the heater surface. This element acts in a well known manner to regulate the supply of heat energy to the resistant element 28. In order to maintain the interior of the heater enclosure at a uniform level, in known manner, the supply of energy to the heating element 28 is varied in order to off-set changes in ambient temperature and variations in in-coming voltage.

As indicated above, yarn passing through the heater may be wrapped one or more times about the heated surface, as may be desired when treating heavy denier yams or in instances where the yarn is passing through the heater at a high rate of speed. The heater includes means for keeping separate from one another several wraps of convolutions of yarn whichconsists of a thin plate 40 having one end mounted in the plate 13 so that the bottom surface of plate 40 lies close to the outer surface of the heated roll. This plate has mounted in it a series of up-standing separating pins 41. Successive wraps of yarn are placed alongside successive pins and thus prevented from overrunning one another.

FIG. 1 of the drawing illustrates a modification of the heater which may be used in heating operations wherein the prolonged contact of yarn with the heater surface is not required. In this instance, an entrance tube similar in form to 29 may be mounted as shown in I dotted lines at 42 and an exit tube as shown in dotted shrinkage of the yarn in contact with the heater surface when the yarn is processed at temperatures and tensions which cause shrinkage.

FIG. 4 illustrates a heater similar in construction to that shown in FIGS. 1 and 2 except that it is provided with pencil Calrods for adding head energy directly to the heat sink 21. These Calrods 66, 67 (resistance heating elements) are mounted in aligned apertures in the plate 13 and the heat sink 21. Such an additional source of heat to the heater enclosure may be a desirable complement to that supplied by the exterior heating element 28, but in the instance where the additional supply is used, the temperature of the atmosphere surrounding the heated roll is nevertheless maintained at least as high as that of the surface of the roll as explained earlier with reference to FIGS. 1 and 2. The element 66, 67 may be used, for example, to supply heat energy to the extent that they alone will be capable of raising the temperature of the heated surface to a certain steady level somewhat below the desired yarn treatment temperature, the remainder of the energy required being supplied from a source external to the heated roll. I

FIG. shows a modification of a heated surface which may be used in lieu of the roll shown in FIGS. 1 and 2. Two space rollers 68, 69 are rotably supported by shafts70, 71 which extend through openings in the plate 13. The rollers are slightly skewed so that a plurality of convolutions of yarn Y", as illustrated, and will remain spaced from one another on the surfaces of the rollers. The shafts 70, 71 respectively carry the drive pulleys 72, 73 which are engaged by a belt 74 which is driven by pulley 75 on the drive shaft 76. This drive shaft is rotated by means including a gear 77 which is designed to engage driving means provided on the machine with which the heater is associated.

FIG. 6 illustrates another type of heated surface which may be employed in heaters according to the present invention, FIG. 6 being a front view to better illustrate a typical yarn path- The heater surface comprises parts of the peripheral surfacesof four cylinders which 'are'rotably supported in the plate 13, in the manner of cylinders 68, and 69 as shown in'FIG. 5. The incoming yarn first engages a small angular portion of the periphery of cylinder 78 and then proceeds around a somewhat larger portion of the periphery of cylinder 79 and around progressively larger portions of cylinders 80 and 81. It will be observed that this arrangement does not obstruct shrinkage of the in-coming yarn since its contact with the periphery of cylinders 78 and 79 is at shallow angles. However, since a large part of the shrinkage will have occurred at the time the yarn makes contact with the cylinder 80, the angular contact with this cylinder and with cylinder 81 is substantially increased. In brief, the arrangement is such that the yarn's contact with the heater surface is minimized initially to avoid drag which would interfere with shrinkage and the area of contact increased to permit better heating once the shrinkage causing the drag is relatively completeRolls 78, 79, 80, and 81 may also be driven at different peripheral speeds to provide for different yarn tension between rolls to permit shrinkage or cause stretching as is sometimes required.

FIGS. 7-11 illustrate some of the different kinds of textile yarn processing machines in which the heater according to the present invention may be used.

FIG. 7 schematically illustrates the arrangement of a false twisting machine wherein flat producers yarn such as nylon or Dacron is drawn from a pirn 44, passed through a pretensioning device 45 and then engaged by a set of feed rolls or nip rolls 46. The yarn then passes through the heater H and thence through a false twisting spindle 47. The false twist inserted by the spindle 47 runs downstream through the heater and is stopped at the rolls 46. Twisted yarn is heated in the heater and then cooled in the region between the false twist spindle and the heater while still in its twisted condition. The twist is removed from the yarn as it passes out of the spindle 47 whereupon it is engaged by a second set of feed or nip rolls 48 which cooperate in determining the tension at which the processed yarn is wound upon the takeup package 49. Also the relative speeds of the rolls 46 and 48 determines the tension upon the yarn being twisted. Present day false twist machines are capable of processing yarn at the rate of -140 yards per minute and at such operating speeds it has been found necessary to employ contact heaters which may be as much as four feet in length. As indicated earlier the efficiency of such heaters is diminished in part because of the vibratory contact between the heater surface and the twisting yarn, and also because the atmosphere surrounding all parts of the yarn except that in tangential contact with the heater surface is at a somewhat lower temperature than the heater surface. These disadvantages do not exist in a false twisting machine which employs a heater according to the present invention. The yarn entering the heater is disposed around the surface of the rotating heater roll 16 which is advancing at the same rate as the yarn thereby avoiding relative movement which causes a vibratory effect. With no vibration, the yarn remains in contact with the surface of the rotating heater so that more filaments of the yarn are in effective heat transfer relationship with the surface. In addition, the heated atmosphere in contact with portions of the yarn which are not disposed against the heater are constantly swept by the circulating air so that in the course of the passage of the yarn through the heater it is contacted by a large volume of hot air moving with or counter to the direction of the yarn being heated. The heater according to the present invention also provides a preheating zone including the tube 29 in which the yarn may be permitted to shrink as is sometimes desired in false twist processing. The degree of shrinkage occurring in this region may be regulated by the relative speeds of the revolving heater roll and the nip rolls 46. The heater also provides a Zone including the tube 29A in which the yarn, free of obstruction, may accept twist passing backwardly from the spindle 47. The twist may be trapped as desired at any point within the heater but is preferably trapped near the point at which the exiting yarn leaves contact with the heated roll. If unobstructed, the twist may tend to travel back different distances around the roll but such variations may be avoided by trapping the twist in advance of the point to which it at all times extends. This may be done by means of a twist trapper such as illustrated in FIGS. 12 and 13. This device consists of a frame 151 as shown in FIG. 14 which is adapted to snap down over separator pins 41. Two arms 151, 152 are supported on the frame and have a twist trap wheel 53 journaled between them. when the twist trapping device is in position on the separator pins springs 15A, hold the wheel 153 in firm contact with the surface of the heater roll, as illustrated in FIG. 12. The twist trapper is positioned so that the wheel will overlie a wrap of the yarn and thus trap the twist by pinching the yarn between the heater surface and the wheel 153. It is apparent that the twist trapper may be mounted in other ways and may consist of a heat proof belt running in contact with the surface of the heated roll.

FIG. 8 schematically illustrates a machine of the kind in which flat producers yarn such as Dacron or nylon is first false twisted and then post treated for the purpose of producing a set yarn. The false twist portion of this operation is the same as that illustrated in FIG. 7 up to the feed rolls 48 and these elements where shown in FIG. 8 are numbered to correspond. In a machine of the kind shown in FIG. 8 the yarn passes from feed rolls 48 through a heater H of the kind illustrated and described herein. The stretch yarn being forwarded by the feed rolls 48 may have an extensability of 300-500 percent but is in straightened condition as it arrives at feed rolls 48. The peripheral speed of the feed rolls 48 and the heater roll are adjusted so as to provide an overfeed of from 3 to 20 percent for example. Consequently, the yarn arriving on the surface of the heater roll is partially relaxed and is maintained in this condition on the surface of the roll. Even though under light tension, the yarn remains in firm contact with the roll and is somewhat spread out in addition thus increasing the efficiency of heat transfer by conductance. As explained with reference to the false twisting machine, the efficiency of heating is further improved by the rapid circulation of heated air within the enclosure. Yarn passing from the second stage heater is engaged by the feed rolls 50 and passed to the takeup package 51. It is apparent that due to the nature of the heater construction various conditions of tension can be established between the heater and the feed rolls 50.

FIG. 9 illustrates a machine including the heater of the present invention which may be employed simultaneously to twist and post-treat false twist yarn. Thermoplastic false twist yarn is drawn from the revolving supply spool 52 and passed upwardly through a guide 53 to a set of feed rolls S4. A desired degree of overfeed of the yarn to the heater between feed rolls 54 and the revolving roll of the heater is established'as described with respect to FIG. 8. Post treated yarn is then gathered on the takeup package 55.

FIGS. and 11 illustrate the manner in which a heater according to the present invention may be used on constant speed coneing machines also suitable for the post treatment of torque stretch yarn. Referring to FIG. 10, a package of wholly synthetic false twisted thermoplastic yarn such as nylon or Dacron is indicated at 56. This yarn is drawn through a guide 57 to feed rolls 58. The yam then passes through heater H. The desired overfeed to the heater is established between the revolving roll thereof and the feed rolls 58. The treated yarn then passes tothe feed rolls 59 and thence to the conical takeup package 60. The arrangement shown in FIG. 11 is similar to that of FIG. 10 except that the supply package of false twist yarn is mounted on a two-for-one twist spindle. The yarn is drawn through the guide 62 to the feed rolls 63 thence through the heater H and through the feed rolls 64 to the conical takeup package 65. Each of the arrangements of FIGS. 9-11 entail the advantages described earlier with respect to the apparatus illustrated in FIGS.

7, and 8, and in all instances the heaters H and preceded in the path of yarn travel by a pair of nip or feed rolls.

FIGS. 15-17 are views of a heater roll which may be used in lieu of the one shown in FIGS. 1, 2 and 4. This roll comprises a perforate surface such as may be made from a fine metal or glass screeen and has in its interior squirrel-cage like blades which force air through the perforate surface when the heater roll is rotated. Referring to FIG. 15, the screen surface of the roll is indicated at 82. The front end of the roll carries fan blades 83 which cause circulation and agitation of the air within the enclosure as heretofore explained. FIG. 16 is a rear view of the same roller showing an end plate 84 in which the squirrel-cage type blades 85 are mounted and through which the driving shaft 86 passes. The shaft 86 is provided with a gear (not shown) which is designed to be enagaged by a driving element on the textile machine with which the heater is associated. FIG. 17 is a front elevational view of the same heater roll showing a ring 87 in which the forward ends of the blades 85 are supported and which supports the outer end of the fan blades 83. The shaft 86 also carries a flanged ring 88 at its distal end to which the inner ends of the fan blades 83 are fixed. It will be apparent that a perforate surface heater roll of the kind described can be altered in particulars so that the heated atmosphere is passed inwardly or outwardly through the perforate surface. It will also be apparent that when the air is being drawn through the surface that the yarn thereon will be subjected to a flow of heated air through the yarn and will also be forced into firmer contact with the surface itself, thereby improving the heat transfer to the yarn in both respects.

FIG. 18 illustrates a further kind of heater surface which may be employed. This comprises two cylinders 89, 90 which are rotably supported in the plate 13. These cylinders support a belt which provides the contact heater surface. The belt is formed of metal or any other material which will provide good heat conduction to the yarn passing in contact with it. A yarn separator bar and pin assembly 92 is mounted adjacent the belt to maintain separate convolutions of the yarn running in contact with the heater surface. This element is similar in form and function to the assembly 40, 41 described with reference to FIG. 2. The means for driving the heater surface is similar to that described earlier with respect to FIG. 5.

FIG. 19 discloses an arrangement in which the fan blade associated with a heater roll is constructed so that it may be turned in a direction opposite to that in which the roll is moving. This arrangement would be applicable to the type of heater roll disclosed in FIGS. 1 and 2 and FIG. 15. A fan 93 is shown mounted on a shaft 94 which is concentric within the shaft 95 which is connected to and drives the heater roll 96. It should be observed that such an arrangement of fan may be employed with the cylinder 89, 90 illustrated in FIG. 16, the cylinders 68, 69 of FIG. 5 and also cylinders 78-81 of FIG. 6. Similarly, a fan of the type illustrated in FIG. 3 may be fixedly attached to the end of any one of the specified cylinders.

FIG. 20 is a schematic illustration of a Godet type self-advancing roll 97. The construction of such a roll is well understood in the art and no further descriptions seem required. This type of roll may, however, be used in the heater of the present invention in lieu of the kind shown in FIGS. 12.

FIG. 21 illustrates schematically another form of heater according to the present invention. This heater involves the application of the same principles as explained with reference to the heaters of FIGS. 1-2 but is provided with two separate yarn treatment zones in which yarn passing through the heater may be subjected to different treatment conditions. The enclosure 98 may be formed in the same manner as enclosure of FIG.-1. The enclosure may be somewhat elongated as compared to that of FIG. 1 and is separated into two distinct zones 99 and 100 by an insulated plate 101. A heater roll 102 which may be of the kind illustrated in FIGS. 1 and 2 of the drawings, is mounted in the zone 100. A resistance heating element 103 is mounted in the upper zone 99. The insulated plate is provided with an aperture 104 through which the yarn passes from one zone to the other. There is also provided a U- shaped pipe 105 which at one end extends through the enclosure into the upper zone 99 and at the lower end into the zone 100. This pipe is provided with a regulator valve 106 by means of which the quantity of air flowing from one zone to the other may be regulated. Rotation of the roll 102 will cause the fan associated with it to draw air through the pipe 105 from the zone 99 in which the heating element is located into the lower zone 100. In the course of passing through the exposed. pipe the heated air drops in temperature so that the air being circulated into the chamber in which the heated roll is located is at a lower level of temperature than the zone 99. The pipe 105 is slidably mounted in the enclosure walls so that a greater length of it may be exposed to the ambient atmosphere, and thus increasing or decreasing the temperature drop of the air traveling through it. The valve 106 may also assist in regulating the temperature which will be established in the lower zone 100. Air drawn into the zone 100 may be returned to the upper chamber 99 through a small discharge aperture 107.

' It'is apparent that the condensing and filtering tube 31 shown in FIG. 1 may be adapted to perform the function of the tube 105 in the arrangement of FIG. 21 or alternatively, that by the addition-of a spin finish collecting'tube 108,'indicated in dotted lines'on FIG. 21, the tube 105 may. also serve as the condensing and filtering means.

It is understood of course that the heater of FIG. 21 may be equipped with the exit and entrance tubes, baffles, thread separator and the electrical controls which have been illustrated and described with respect to FIG. 1. V

The heater of FIG. 21 may be used advantageously in a false twisting machine. The yarn Y may be permitted to shrink as it approaches the roll 102 and then wrapped one or more times around the roll while exposed to a temperature in the zone 100 of about 300-325 F. for example. The yarn may be then passed through the aperture 104 into the zone99 where it may then be subjected to a temperature of 440 F. for example. The false twist in the yarn may be stopped in the heater, as earlier described, or thereafter.

- FIG. 22 illustrates the same heater as shown in FIG. 21 except that it has been altered so as to permit a cooling of the yarn in the course of its travel through the heater. The enclosure wall is provided with an aperture 108 which is about level with the top of the roll 102.

The yarn is led through this aperture around a roller 109 and then back through the aperture into contact with the periphery of the guide roller 110. The roll is positioned so that the yarn leaving it is directly beneath the aperture 104 in the insulated plate. In this arrangement the yarn may be shrunk, passed one or more times around the roll 102 to treat it under given conditions of temperature and tension and then cooled before subjecting it to a second treatment under different conditions in the upper zone 99. It will be apparent that the arrangement for cooling the yarn including the rolls 109 and 110 may be positioned immediately above the insulated plate 101 instead of beneath it, and that either of these rolls may be driven in a desired manner in order to achieve different levels of tension, as de sired, in the yarn traveling through the heater.

We claim:

1. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating said surface and said atmosphere so as to preclude a descending temperature gradient in said atmosphere in the direction away from said surface when yarn is being heated and mechanical means for circulating said atmosphere within said enclosure to continuously sweep away from the yarn a portion of said atmosphere which has delivered up some part of its heat energy to the yarn, said surface being continuously movable and being associated with means for moving it in the direction of travel of the yarn passing through said heater in contact with said surfaces, wherein said surface is the peripheral surface of a rotatable element which is circular in cross-section and carries means for circulating said atmosphere within the enclosed heater.

2. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating said surface and said atmosphere so as to preclude a descending temperature gradient in said atmosphere in the direction away from said surface when yarn is being heated and mechanical means'for circulating said atmosphere within said enclosure to continuously sweep away from the yarn a portion of said atmosphere which has delivered up somepart of its heat energy to the yarn, said surface being continuously movable and being associated with means for moving it in the direction of travel of the yarn passing through said heater in contact with said surfaces, wherein the yarn heater is for a false-twist machine which includes a freely rotatable element mounted to press against said surface and a portion of the yarn traveling in contact with said surface and to be rotated thereby, whereby said rotatable element is capable of arresting-movement of any false-twist in the yarn that may arrive at said element.

3. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the direction away from the said surface when yarn is being heated including means for condensing spin-finish and other volatiles out of circulating heated atmosphere within the heater enclosure including a tube communicating at either end with the interior of said enclosure and having an intermediate section extending into a zone of temperature lower than that at which spinfinish and said volatiles condense.

4. A yarn heater as claimed in claim 3 in which said condensing means also comprises means for filtering solids out of the atmosphere circulating through said tube.

5. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the direction away from the said surface when yarn is being heated, said surface being continuously moveable and being associated with means for moving it in the direction of travel of the yarn passing through said heater in contact with said surface in which said surface is the surface of a belt running over two spaced-apart rotatable pulley elements.

6. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the atmosphere in the direction away from the said surface when yarn is being heated, and wherein said surface is porous and wherein the heater includes means to force said heated atmosphere through said porous surface, whereby yam passing in contact with said surface is placed in more effective heat exchange relationship with said surface and said heated atmosphere.

7. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere in the direction away from the said surface when yarn is being heated with said heater enclosure extending beyond said surface to provide an enclosed space in which the yarn is maintained at an elevated temperature by said heated atmosphere, and in which space is positioned means for arresting twist running back from a false-twist device positioned downstream from said heater.

8. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith, both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the di- 9. An enclosed heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the direction away from the said surface when yarn is being heated, said heating means including an additional source of heat associated with said surface for aiding in elevating the temperature of said surface and also including means for independently regulating the supplyof energy to said first source of heat and said additional source of heat.

10. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith, both of which simultaneously contact yarn being heated at least during a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the direction away from said surface when yarn is being heated, said surface being continuously moveable and being associated with means for moving it in the direction of travel of the yarn passing through said heater in contact with said surface, said heater further including a bar extending transversely of the direction of yarn travel on said surface and provided with means to engage each of several wraps of the yarn around said endless surface and maintain each wrap in a selected sepa rate position on said surface, said bar being faired into the said surface.

11. A method of heating a travelling textile yarn which comprises the steps of moving a yarn in contact with a porous heat conductive surface on one portion of the yarn profile and with a gaseous atmosphere in contact with the'remainer while passing it through an enclosure and heating the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in a direction away from said surface, and including the step of circulating the heated atmosphere within the heated enclosure by mechanical means, so that the heated atmosphere is circulated through the surface with which the yarn is in contact.

12. A heater comprising an enclosure and insulated means separating the enclosure into a first and second chamber, said first chamber comprising a heat conductive surface and a first gaseous atmosphere in contact therewith both of which simultaneously contact yam being heated during at least a portion of its passage through the heater, said second chamber being free of any heat conductive surfaces and having a second gaseous atmosphere in free communication with said first gaseous atmosphere and in contact with said yarn, means for heating the said surface and the said first atmosphere so as to preclude a descending temperature gradient in the said first atmosphere in the direction away from the said surface when yarn is being heated, separate means for heating the said second atmosphere, said enclosure and insulated means being provided with openings whereby yarn may be introduced into said first chamber, passed to said second chamber and then withdrawn from the second chamber.

13. A heater as claimed in claim 12 wherein the enclosure is provided with means whereby yam can be withdrawn, cooled and returned to the enclosure in the course of its travel through the heater. 

1. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating said surface and said atmosphere so as to preclude a descending temperature gradient in said atmosphere in the direction away from said surface when yarn is being heated and mechanical means for circulating said atmosphere within said enclosure to continuously sweep away from the yarn a portion of said atmosphere which has delivered up some part of its heat energy to the yarn, said surface being continuously movable and being associated with means for moving it in the direction of travel of the yarn passing through said heater in contact with said surfaces, wherein said surface is the peripheral surface of a rotatable element which is circular in cross-section and carries means for circulating said atmosphere within the enclosed heater.
 2. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating said surface and said atmosphere so as to preclude a descending temperature gradient in said atmosphere in the direction away from said surface when yarn is being heated and mechanical means for circulating said atmosphere within said enclosure to continuously sweep away from the yarn a portion of said atmosphere which has delivered up some part of its heat energy to the yarn, said surface being continuously movable and being associated with means for moving it in the direction of travel of the yarn passing through said heater in contact with said surfaces, wherein the yarn heater is for a false-twist machine which includes a freely rotatable element mounted to press against said surface and a portion of the yarn traveling in contact with said surface and to be rotated thereby, whereby said rotatable element is capable of arresting movement of any false-twist in the yarn that may arrive at said element.
 3. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the direction away from the said surface when yarn is being heated including means for condensing spin-finish and other volatiles out of circulating heated atmosphere within the heater enclosure including a tube communicating at either end with the interior of said enclosure and having an intermediate section extenDing into a zone of temperature lower than that at which spin-finish and said volatiles condense.
 4. A yarn heater as claimed in claim 3 in which said condensing means also comprises means for filtering solids out of the atmosphere circulating through said tube.
 5. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the direction away from the said surface when yarn is being heated, said surface being continuously moveable and being associated with means for moving it in the direction of travel of the yarn passing through said heater in contact with said surface in which said surface is the surface of a belt running over two spaced-apart rotatable pulley elements.
 6. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the atmosphere in the direction away from the said surface when yarn is being heated, and wherein said surface is porous and wherein the heater includes means to force said heated atmosphere through said porous surface, whereby yarn passing in contact with said surface is placed in more effective heat exchange relationship with said surface and said heated atmosphere.
 7. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere in the direction away from the said surface when yarn is being heated with said heater enclosure extending beyond said surface to provide an enclosed space in which the yarn is maintained at an elevated temperature by said heated atmosphere, and in which space is positioned means for arresting twist running back from a false-twist device positioned downstream from said heater.
 8. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith, both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the direction away from the said surface when yarn is being heated, said heater including a tube communicating with and extending outwardly from the heater enclosure and through which the yarn enters the heater enclosure, the tube being mounted with respect to the enclosure to align its axis tangentially to said surface and including means for establishing a heated atmosphere within said tube.
 9. An enclosed heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the direction away from the said surface when yarn is being heated, said heating means including an additional source of heat associated with said surface for aiding in elevating the temperature of said surface and also including means for independently regulating the supply of energy to said first source of heat and said additional source of heat.
 10. An enclosed yarn heater comprising a heat conductive surface and a gaseous atmosphere in contact therewith, both of which simultaneously contact yarn being heated at least during a portion of its pAssage through the heater, means for heating the said surface and the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in the direction away from said surface when yarn is being heated, said surface being continuously moveable and being associated with means for moving it in the direction of travel of the yarn passing through said heater in contact with said surface, said heater further including a bar extending transversely of the direction of yarn travel on said surface and provided with means to engage each of several wraps of the yarn around said endless surface and maintain each wrap in a selected separate position on said surface, said bar being faired into the said surface.
 11. A method of heating a travelling textile yarn which comprises the steps of moving a yarn in contact with a porous heat conductive surface on one portion of the yarn profile and with a gaseous atmosphere in contact with the remainer while passing it through an enclosure and heating the said atmosphere so as to preclude a descending temperature gradient in the said atmosphere in a direction away from said surface, and including the step of circulating the heated atmosphere within the heated enclosure by mechanical means, so that the heated atmosphere is circulated through the surface with which the yarn is in contact.
 12. A heater comprising an enclosure and insulated means separating the enclosure into a first and second chamber, said first chamber comprising a heat conductive surface and a first gaseous atmosphere in contact therewith both of which simultaneously contact yarn being heated during at least a portion of its passage through the heater, said second chamber being free of any heat conductive surfaces and having a second gaseous atmosphere in free communication with said first gaseous atmosphere and in contact with said yarn, means for heating the said surface and the said first atmosphere so as to preclude a descending temperature gradient in the said first atmosphere in the direction away from the said surface when yarn is being heated, separate means for heating the said second atmosphere, said enclosure and insulated means being provided with openings whereby yarn may be introduced into said first chamber, passed to said second chamber and then withdrawn from the second chamber.
 13. A heater as claimed in claim 12 wherein the enclosure is provided with means whereby yarn can be withdrawn, cooled and returned to the enclosure in the course of its travel through the heater. 